Re: Correction : EMC symetrix - 1M stripe width - Raid 0+

I agree with Don. We have always found it better to mirror at the EMC Symmetrix level and then handle striping requirements via the volume manager (such as Veritas Volume Manager). In fact, I presented a paper on this at IOUG-A last year.

The bottom line is to make sure that you properly design it. Just because it's on an EMC doesn't mean that you shouldn't build the system as optimally as possible. If you optimize the system and use the EMC intelligence and caching to enhance your performance, you'll get much better results than resoring to "cache-based tuning". If you tune based on cache, then the only way you'll ever be able to optimize is to buy more and more cache . . .which, of course, costs you cash. :-)

Don Granaman wrote:

> I have used the Symmetrix with hardware mirroring and software
> (Veritas Volume Manager) striping and seen significant performance
> gains over just mirroring in the Sym. It is going to depend a lot on
> your I/O patterns and volume though.
>
> I have used SAME, but in general wouldn't really recommend it for most
> systems (based on the concept though, not the stripe size). Sure it
> is "easy", but it isn't usually optimal. (If this is the "same" SAME
> I am thinking of - stripe and mirror everything across everything.)
> The EMC cache will buy a lot, but in the most demanding systems it is
> still important to segregate some physical I/O to distinct
> disks/disksets to reduce contention - and in the case of EMC, to
> better utilize the cache.
>
> I agree whole-heartedly on PowerPath!
>
> As always, I would recommend reading Gaja's paper at
> http://www.quest.com/whitepapers/Raid1.pdf
>
> -Don Granaman
> [OraSaurus]
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Wednesday, November 14, 2001 10:15 AM
>
> > We're using the Symetrix storage system as well, but we did not use
> stripping,
> > but full mirroring instead. Performance has been more than
> acceptable, but we
> > really haven't pushed it I think. As far as the SAME (Stripe And
> Mirror
> > Everything) idea from Oracle, that's great if you have the funds and
> space for
> > all of those disk systems. Otherwise it's 'pie in the sky'. BTW,
> you SHOULD
> > look into EMC's PowerPath software (if available on your system).
> This one
> > allows the computer to balance IO across all of the ports available
> into the
> > Symetrix. It really does improve matters.
> >
> > Dick Goulet
> >
> > ____________________Reply Separator____________________
> > Author: =?iso-8859-1?q?Connor=20McDonald?= <hamcdc_at_yahoo.co.uk>
> > Date: 11/14/2001 2:10 AM
> >
> > Interestingly you could go back to Oracle support and
> > ask them about the "SAME" method (as presented by an
> > Oracle employee if I recall correctly at a user
> > conference) - which advocated 1m stripes.
> >
> > You'll tend to face these battles with EMC - their
> > sales people are great at things like "you don't need
> > to worry about where things are on the disk, or
> > striping etc - our cache takes care of all of
> > that"...Yeah right!
> >
> > As a general guideline, I think you'd be better of
> > with smaller stripe size, but you don't have to limit
> > yourself - you could have fine granined striping for
> > some parts of the system, and larger grains for other
> > parts.
> >
> > hth
> > connor
> >
> > --- Mohammed.Ahsanuddin_at_VerizonWireless.com wrote: >
> > Hi,
> > >
> > > Application : OLTP
> > > Environment : Solaris 2.6 on a E10K
> > > Database : 8.0.5.2.1
> > >
> > > We recently migrated from sun a5200 storage to EMC
> > > symetrix, and we have
> > > been seeing occasional performance problems. When
> > > contacted, Oracle support
> > > among other things pointed out the stripe width we
> > > have used 1M, is very
> > > large and also said users will not see an advantage
> > > above 64K.
> > >
> > > When we had Sun storage before we had 64K as the
> > > stripe width.
> > >
> > > Has anyone faced this kind of issue or has any
> > > comments..or can someone
> > > explain the low level impact of the stripe width on
> > > the ORACLE I/O
> > > operations?
> > >
> > > Much appreciated..
> > >
> > > Regards
> > >
> > > Mohammed Ahsanuddin
> > > Oracle DBA
> > > --
> > > Please see the official ORACLE-L FAQ:
> > > http://www.orafaq.com
> > > --
> > > Author:
> > > INET: Mohammed.Ahsanuddin_at_VerizonWireless.com
> > >
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Byron Pearce                         mailto:bpearce_at_tenure.com
Tenure Systems, Inc.                 Arlington, Texas

"It's hard to be a ninja when you wear a beeper."


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